1. Field of the Invention
The present invention relates generally to a composite roofing product and a method and apparatus for making the composite roofing product which product includes a synthetic rubber or thermoplastic sheet and a fabric matting adhered together via a polymeric film or other uniformly applied hot melt adhesive.
2. Description of the Related Art
Continuous sheet roofing products have been increasingly used in commercial building applications which involve large roof expanses, particularly with flat or shallow pitched roofs. This popularity of sheet roofing is due to a variety of factors, including convenience and speed of installation, reduced material and labor costs and longevity and reliability of the installed roof. Many sheet roofing products include synthetic rubber or thermoplastic sheets which are applied from rolls and attached to the roof via a variety of adhesives and fasteners.
While synthetic rubber or thermoplastic sheets offer a number of advantages over competing products, including good weather resistance and elasticity, such rubber or thermoplastic sheets, in and of themselves are not very resistant to puncture or stress cracking. Furthermore, rubber or thermoplastic sheets, with their relatively smooth and moisture impervious surfaces, are resistant to bonding by most conventional adhesives, presenting a problem in reliably adhering the rubber or thermoplastic sheets to the roof surface. Finally, where contiguous rolls of rubber or thermoplastic sheets meet, they must overlap each other to form a weather impervious seal but these joints create a potential problem area where the overlapped rubber seams are adhered.
Previous attempts have been made to produce a composite roofing material including a synthetic rubber or thermoplastic sheet with a fabric backing adhered thereto. One such roofing material is a membrane including a synthetic rubber or thermoplastic sheet having a thickness of from 40-70 mils backed by a polyester fleece-like matting having a thickness of about 40-80 mils which is produced by the Colonial Rubber Company of Dyersburg, Tennessee. This product has proven to be very durable and crack and puncture resistant. In addition, the fleece-like matting provides an ideal bonding surface for roofing adhesives, such as the polyurethane foam adhesive taught in U.S. Pat. No. 4,996,812 (the '812 patent) to the present inventor, as well as asphalt and other adhesives.
Mass production of this composite material has proven to be problematical, however. In the known production method, the fleece-like matting is adhered to the rubber or thermoplastic sheet during the vulcanization process, thus substantially complicating the vulcanization process and requiring very expensive, dedicated production machinery. At least partially as a result of the complexity of the process and equipment, material waste averages in excess of 30%. Since the membrane product is produced during the vulcanization process, the wasted material has virtually no other use. Furthermore, it has proven impossible to produce a membrane with a selvedge on the underside of the membrane between the outside edge of the rubber or thermoplastic sheet and the polyester matting. This is because, if such a selvedge is left, once the membrane is rolled into a roll for vulcanizing, the exposed selvedges will stick to adjacent layers in the roll, thus resulting in a congealed mass.
It is clear then, that a need exists for an economical and reliable method of producing a composite roofing material including a flexible sheet backed by a fleece-like matting. Such a method should preferably use existing rolls of synthetic (such as EPDM) rubber, which are available in commodity quantities, and should produce a roofing material with minimal waste. The roofing material thus produced should preferably include a selvedge on each side of the material underside between the edge of the rubber or thermoplastic sheet and the matting for facilitating the attachment of sealing tape or adhesive between adjacent sheets as they are applied to a roof surface. An apparatus for producing the composite roofing material should be relatively economical to make and to run, and should be capable of producing large quantities of finished roofing material with minimal waste and a clean talc-free surface to adhere to.